Studies on the role of the pineal gland in the regulation of TSH secretion in postpuberal male rats.
The role of the pineal gland in the regulation of thyroid-stimulating hormone (TSH) secretion was studied in postpuberal male rats using 12:12 h light:dark cycles. Pinealectomy, performed 3--4 days before decapitation, had no effect on the basal or thyrotropin-releasing hormone stimulated TSH secretion, but significantly decreased the cold-induced TSH response both at noon and at midnight. Neither hypothalamic thyrotropin-releasing hormone concentrations nor serum thyroid hormone levels were affected by pinealectomy. Melatonin injected intravenously (1 and 10 mg/kg) or intracerebroventricularly (5 and 50 microgram/rat) had no effect on the basal or cold-stimulated TSH levels, neither was the thyrotropin-releasing hormone induced (50 and 125 ng/rat i.p.) TSH response modified by melatonin (1 mg/kg i.v.). Arginine vasotocin (1 and 100 ng/rat) given intracerebroventricularly had no effect on the basal or cold-stimulated TSH secretion. These results suggest that the pineal has no influence on the basal activity of the hypothalamus-pituitary-thyroid system, but it seems that the cold-induced TSH response depends to a considerable degree on the intact pineal gland.
D000818:Animals; D007031:Hypothalamus / Q000187:drug effects; D008297:Male; D008550:Melatonin / Q000494:pharmacology; D010870:Pineal Gland / Q000502:physiology*; D010902:Pituitary Gland / Q000187:drug effects; D051381:Rats; D013972:Thyrotropin / Q000378:metabolism*; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood; D014668:Vasotocin / Q000494:pharmacology
D014284:Triiodothyronine; D013973:Thyrotropin-Releasing Hormone; D013972:Thyrotropin; D008550:Melatonin; D013974:Thyroxine; D014668:Vasotocin